Expansion
Physics · प्रसार · 15 facts
Thermal expansion: substances expand on heating, contract on cooling
Solids: linear, superficial, cubical expansion
Railway tracks have gaps for summer expansion
Electric wires sag in summer, tighten in winter
Anomalous expansion: water expands cooling from 4C to 0C
Water max density at 4C; aquatic life survives in frozen lakes
Bimetallic strip: two metals bonded, bends on heating (thermostat)
Gases expand most; liquids more than solids for same temp rise
Hot glass cracks with cold water (uneven expansion)
Bridges use roller supports; roads have expansion joints
Coefficient of linear expansion (alpha): change in length per unit length per degree
Invar alloy: very low coefficient of expansion; used in precision instruments
Gas expands more than liquid at same temperature rise (gases most, solids least)
Pendulum clock runs slow in summer (rod expands, period increases)
Rivet joints use expansion: hot rivet cools and contracts, pulling metal sheets tight